1. Field of the Invention
The present invention is directed to forming rigid three-dimensional articles from a precursor, planar, source of fiber-reinforced resin matrix by use of stitching and sewing techniques to connect the planar source sheet into an intermediate three-dimensional preform. The source material is preferably in a B-stage state of cure during the stitching and sewing operation and is subsequently rigidified by physical and/or chemical stimuli.
2. Background of the Invention
Composite structures of a fiber-reinforced, polymeric matrix, have found utility for various structural articles.
One such method of manufacturing comprises impregnating woven fabric with a curable resin in liquid form and "laying-up" said "wet" material onto a mold or core. The wet laid-up material can be cured by applied heat and pressure, typically a slow autoclave process. Alternatively, continuous filaments or fibers can be "chopped" and fed into the path of a projected stream or spray of liquid resin which coats the chopped filaments or fibers while simultaneously entraining and conveying the chopped fibers or filaments onto a mold surface. Such chopped filaments techniques are not suitable for articles requiring uniformly distributed or oriented reinforcement.
Still other manufacturing methods lay-up a dry fabric onto a core, temporarily attaching the fabric to the core by an adhesive or cement applied to the periphery of the fabric pieces. For complex three dimensional shapes, the laying-up of dry fabric pieces on a core and temporarily gluing the edges of the pieces is a time-consuming procedure requiring the use of skilled labor to position and attach the fabric pieces to the core. After the dry fabric pieces are completely laid-up, the core is placed in a mold and a liquid resin is introduced into the cavity between core and mold so as to coat the fabric, flowing through the interstices of the fabric. However, if the liquid resin is introduced into such cavities under pressure, the introduction of the liquid resin may disrupt or dislodge the laid-up dry fabric temporarily adhered to the core causing imperfections, such as overlapped fabric or voids in the fabric reinforcement resulting in an imperfect product or a reject. Once the impregnating resin is cured. recycling of the rejects is impracticable resulting in a loss of both labor and materials.
Thus, there exists a continuing need to provide a simple, economical method of manufacturing three-dimensional shaped composite articles which do not require skilled labor to lay-up individual fabric pieces (whether impregnated with resin or dry fabric).
Additionally, there continues to be a need for a manufacturing method of fabricating three-dimensional shapes at one location, i.e., a factory, but delaying onset of rigidification of such articles until they are placed in situ, i.e., at the site of ultimate use.
Up until the present invention there still existed a need for forming structural units, such as buildings, or components thereof, produced from reinforced resin-composites in an inexpensive manner, which are low in cost not only in the manufacturing thereof but also in the transportation and erection thereof, on site.
Achievement of the foregoing and other objects will become apparent to those of ordinary skill in the art from reading this disclosure.